Description:

Similar in calling convention to IPC::Open3, pipeline() spawns N children,
connecting the first child to the FIRST_CHLD_IN handle, the final child to
LAST_CHLD_OUT, and each child to a shared standard error handle,
CHILDREN_ERR. Each subsequent filter specified causes a new process to be
fork()ed. Each process is linked to the last with a file descriptor pair
created by pipe(), using dup2() to chain each process' standard input to
the last standard output.

FEATURES
IPC::Pipeline accepts external commands to be executed in the form of
ARRAY references containing the command name and each argument, as well
as CODE references that are executed within their own processes as
well, each as independent parts of a pipeline.

ARRAY REFS
When a filter is passed in the form of an ARRAY containing an
external system command, each such item is executed in its own
subprocess in the following manner.